I like this question, because I should get better at this myself. Since this sort of thing does require some time and effort, I'll focus on low-hanging fruit - the traits I most want to improve. While we're waiting for someone who has more experience with this, here are two nice articles I found:

http://quantifiedself.com/2011/04/how-to-self-experiment/

http://hplusmagazine.com/2012/11/14/quantified-self-how-to-designing-self-experiments/